OpenEvidence funding: Every round, investor, and valuation (2026)

OpenEvidence is an AI search engine for doctors. A physician types a clinical question, such as the right dose for a patient with failing kidneys, and gets an answer with citations to the medical literature behind it. Verified clinicians use it for free, and the company earns its money from drug and device makers that advertise on the platform.

Founder Daniel Nadler started the company in November 2021 with $5 million of his own money. Since then OpenEvidence has raised six rounds from outside investors, all of it equity, for a total of about $1 billion. The latest, a $250 million round co-led by Andreessen Horowitz and Byers Capital in September 2026, valued it at $15 billion.

Almost all of that money arrived in the 19 months after February 2025, when Sequoia led the company's first institutional round. Every round since has priced OpenEvidence well above the last, as usage among US physicians kept climbing. Let's dive into OpenEvidence's funding history.

OpenEvidence spent its first three years on a small amount of money from people who already knew its founder. Then it raised four large rounds in under a year, each at a higher price, and a fifth in September 2026.

Nadler had already built and sold one AI company. Kensho, a financial analytics startup backed by Goldman Sachs and GV, sold to S&P Global in 2018. He used part of the proceeds to start OpenEvidence with co-founder Zachary Ziegler, a machine learning researcher.

The first outside money came in July 2022, when Nadler opened a $27 million round to people who had backed Kensho. Jim Breyer, Vista Equity Partners co-founder Brian Sheth, and banker Ken Moelis were among them. Forbes reported the round as a Series B, though the company later called its 2025 raise its first institutional round.

That money paid for a small team of researchers and a computing cluster in Nevada. OpenEvidence also joined the Mayo Clinic Platform accelerator in 2023 and raised a small friends-and-family round the same year. The product spread among doctors by word of mouth: by July 2024 it handled about 358,000 clinical consultations a month.

Sequoia led the Series A in February 2025, the first round led by an institutional investor. The company announced it alongside a content deal with the New England Journal of Medicine, which gave OpenEvidence access to the journal's archive back to 1990.

Five months later, GV and Kleiner Perkins co-led the Series B. Sequoia came back, and Coatue, Conviction, Greycroft, and Thrive Capital joined. By then OpenEvidence said more than 40% of US physicians were logging in daily, and monthly consultations had reached 8.5 million.

The Series C followed after only three months. GV led again, and Blackstone, BOND, and Craft Ventures joined the existing backers. Nadler confirmed the round at the HLTH conference in October 2025, when the platform was handling about 15 million consultations a month.

Thrive Capital and DST Global co-led the Series D in January 2026. The company named 17 existing investors that came back, including Nvidia, ICONIQ, and Mayo Clinic, and said its revenue had passed $100 million.

In July 2026, The Information reported that investors had offered about $200 million at a $20 billion valuation. OpenEvidence was unlikely to take it, and the report cited dilution as the reason. Two months later, it raised from Andreessen Horowitz and Byers Capital at a lower price instead.

Forbes reported the September round first, and Nadler confirmed the leads to Becker's Hospital Review. The company has not given the round a letter, and no press release was published. Hospital systems took part, which matches the company's push into enterprise contracts.

OpenEvidence went from a $1 billion valuation to $15 billion in 19 months. The fastest steps came in 2025, when three rounds closed in eight months.

The Series B priced the company at 3.5 times the Series A. The Series C added another 1.7 times, and the Series D doubled it again. The September round was a smaller step up, about 1.25 times the January price, and came in below the $20 billion offer the company had turned away. None of the announcements say whether the figures are pre-money or post-money.

Revenue gives the climb some footing. OpenEvidence passed $100 million in annualized revenue at the end of 2025, and The Information and Bank of America put its run rate at about $300 million by July 2026. At $15 billion, investors are paying roughly 50 times that run rate, for a company that Becker's reports is close to breakeven on cash flow.

There is no Revenue Memo "Who owns" page for OpenEvidence yet, but the ownership is concentrated. Forbes reported in 2025 that Nadler holds roughly 60% of the company and Ziegler about 10%, which leaves outside investors with a minority despite $1 billion of capital. For a sense of scale in AI search, Perplexity's valuation history reached a similar range with a consumer audience rather than a professional one.

OpenEvidence has drawn many of the same firms that back the largest AI labs. Most early investors kept writing checks, so the Series D had more than 20 participants.

Sequoia led the Series A through partner Pat Grady and has joined every round since. It was the firm that turned OpenEvidence from a founder-funded project into a venture-backed company, at a $1 billion price.

GV, Google's venture arm, co-led the Series B and led the Series C. It was also an early backer of Kensho, so the bet was partly on Nadler himself. The fit is close in another way: OpenEvidence is a free search product funded by advertisers, the same model behind Google's attention marketplace.

Kleiner Perkins co-led the Series B, with John Doerr and Mamoon Hamid involved in the deal. Doerr has also invested personally. Kleiner has come back in each round since.

Thrive Capital joined in the Series B and co-led the Series D with DST Global. Both firms are known for large growth-stage checks, and their arrival marked the shift from an early bet to a company priced on revenue.

Andreessen Horowitz and Byers Capital co-led the September 2026 round, the first time either firm led an OpenEvidence deal. Andreessen Horowitz already holds stakes in clinical AI, including Hippocratic AI's patient-facing agents.

Nvidia was named as an investor by the Series D, though the company has not said which round it first joined. The chipmaker invests widely in AI companies that run on its hardware, but no compute deal with OpenEvidence has been disclosed. Its own cap table is the opposite of OpenEvidence's: Nvidia's ownership structure is spread across index funds rather than held by its founder.

Blackstone, Coatue, ICONIQ, Meritech, Alkeon, BOND, Craft Ventures, Conviction, Greycroft, and Goanna round out the venture and crossover investors. Several joined in the Series B or C, and all of them were on the cap table by January 2026.

Mayo Clinic is both an investor and an early partner, since OpenEvidence went through its health-tech accelerator in 2023. Angels include Jim Breyer and Breyer Capital, Ken Moelis, Brian Sheth, and KKR co-founder Henry Kravis. Hospital systems also took part in the September 2026 round, though the company has not named them.

OpenEvidence is cheaper to run than most AI companies of its size. Nadler said in January 2026 that he was "not planning on burning billions of dollars," and the company is close to breakeven.

Nadler said most of the Series D money would go to training new models and paying for compute. In September 2026, OpenEvidence released its own model family, named Osler, Sackett, Snow, and Darwin, and claimed a perfect score on the MedQA medical exam benchmark. Inference runs in part on Baseten's AI model hosting, which counts OpenEvidence among its customers.

The second use of the money is content, and it is the core of the product's credibility. Doctors trust an answer only if it cites the journals they already read, so OpenEvidence has signed licensing deals with NEJM Group, the JAMA Network, and the National Comprehensive Cancer Network.

The list grew in 2026. Wiley added Cochrane reviews and more than 400 journals and books, Springer Nature signed a licensing agreement in August, and Memorial Sloan Kettering connected its OncoKB cancer-genetics database in September. The Series B was raised mainly to expand these partnerships, and the company calls its approach "copyright-friendly."

Advertising pays for everything else. Drug and device makers buy video, banner, and sponsored placements shown to verified clinicians, a slice of the pharma budget that has moved fast toward digital, as healthcare marketing statistics show. The company says its answer engine and ad system are fully separate.

In September 2025, OpenEvidence bought Amaro, a GV-backed advertising technology startup, to build its own ad infrastructure. The price was not disclosed. It is the company's only acquisition so far.

The money has also funded a run of free tools: DeepConsult research reports, the Visits ambient scribe, a HIPAA-compliant calling tool, voice mode, and continuing-education credits. Each one gives doctors another reason to open the app, and gives advertisers more screens.

The newer push is selling to hospitals. Mount Sinai signed the first enterprise deal in March 2026, built into its records system from Epic Systems, the private software giant, and opened access to nurses and pharmacists. Cedars-Sinai, NewYork-Presbyterian, Penn Medicine, and AdventHealth have followed.

OpenEvidence's growth now comes from beyond individual US doctors. Hospital contracts bring in nurses and pharmacists, and a paid enterprise tier without ads is reported to be in development. Abroad, the company says more than half of Canadian physicians use it, and more than 1 million doctors worldwide. It pulled out of the EU and UK in April 2026 because of uncertainty under the EU AI Act.

The product is moving toward specialist models, with oncology first, and toward drug discovery. Nadler told Forbes in September 2026 that he expects a first drug candidate, aimed at rare cancers, in clinical trials before the end of the year, with three to five more in 2027. That would put OpenEvidence alongside companies such as Unlearn's AI clinical trial tools in drug development, a field far from its search roots.

Nadler has said application companies like his will go public after the foundation model labs, and there is no IPO filing. Business Insider has reported acquisition interest. The main risks are trust, competition, and litigation: drug ads next to clinical answers draw scrutiny, Doximity and Wolters Kluwer's UpToDate both sell rival AI tools, and in the Doximity lawsuit OpenEvidence told a federal court in September 2026 that it would not produce internal messages the judge had ordered. The latest $250 million gives it room to build models and drugs without a quick return to the market.

OpenEvidence has raised about $1 billion, all of it equity. That includes $5 million of founder Daniel Nadler's own money and six outside rounds, from a $27 million round in 2022 to a $250 million round in September 2026. The company has not reported any debt.

OpenEvidence's lead investors are Sequoia, GV, Kleiner Perkins, Thrive Capital, DST Global, Andreessen Horowitz, and Byers Capital. Other backers include Nvidia, Blackstone, Coatue, ICONIQ, Conviction, Greycroft, BOND, Craft Ventures, Meritech, Alkeon, and Mayo Clinic, along with angels such as Jim Breyer, Ken Moelis, and Henry Kravis.

OpenEvidence was valued at $15 billion in its September 2026 round. That is up from $12 billion in January 2026, $6 billion in October 2025, and $1 billion in February 2025.

No. OpenEvidence is private and has not filed for an IPO. Its shares are not traded on any stock exchange.

OpenEvidence is controlled by its founders. Forbes reported in 2025 that CEO Daniel Nadler owns roughly 60% and co-founder Zachary Ziegler about 10%. The rest belongs to employees and investors such as Sequoia, GV, Kleiner Perkins, and Thrive Capital, whose exact stakes are not public.